This invention relates generally to television signal unscrambling systems and, specifically, to systems for unscrambling television signals that have their sync signals suppressed.
As mentioned in the copending application, it is well known in both over-the-air and cable television transmissions to encode or scramble the signals to prevent unauthorized use by those not having the requisite decoding equipment. Commonly, scrambling includes suppressing sync signals so that conventional television receiver synchronizing signal circuits are incapable of recovering them. In most instances a pilot signal or other reference is also transmitted to enable the decoding equipment to appropriately reconstruct the synchronizing signal and to key in the proper decoding signals. The invention in the copending application enables regeneration of proper sync signal information from the video information alone, that is without requiring a supplemental pilot or reference signal. As further explained therein, the regenerated sync signals include a field identifier. Some scrambling systems have different timing in the different fields and need to be identified as to field to properly and automatically control the decoding signal generating equipment. It will be appreciated that the decoding signals are in the nature of timing signals and the timing signal generating means often referred to herein and in the claims is interchangeable with decoding signal means.